Production of an aviation or motor fuel or an aviation or motor fuel constituent



Patentecl Sept. 10, 1946 UNITED STATES PATENT OFFICE PRODUCTION OF AN AVIATION OR MOTOR FUEL R AN AVIATION OR ll/IOTOR FUEL CONSTITUENT Stanley Francis Birch, Frederick Arnold Fidler,

Thornes, Sunbury-on- Thames, England, assignors to Anglo-Iranian Oil Company Limited, London, England, a British joint-stock corporation and Leslie Senior No Drawing. Application September 16, 1943, Serial No. 502,644. In Great Britain July 1, 1942 3 Claims. (Cl. 260 -666) polymerised to dicyclopentadiene and in accordance with invention the latter is then depolymerised to produce cyclopentadiene again, and the cyclopentadiene is then hydrogenated to form cyclopentane, a substance having an octane number of 84 (C. F. R. motor method) and thus adapted for use as an aviation or motor fuel or constituent thereof,

The invention has among its objects to produce cyclopentane under conditions of practical convenience and efliciency by the hydrogenation of cyclopentadiene, and to avoid the practical disadvantages attending the reaction due to the considerable amount of heatdeveloped.

According to the invention cyclopentadiene is hydrogenated in the presence of a diluent present in such considerable proportion as to avoid the practical disadvantages usually attending the reaction by reason of the considerable heat evolved under usual reaction conditions, the diluent functioning as a moderating or stabilizing agent.

Thus according to the invention high concentrations of hydrogen may be used as a moderating or stabilising diluent in considerable excess of the small proportion that is consumed in the reaction; or instead of or in addition to high concentrations of hydrogen, benzol or the light ends of the benzol iorerunnings may be used as the diluent, or alternatively or in addition the cyclopentane product of the process may be so used. The use of the light ends as the diluent has moreover the further advantage that its content of benzene is refined in the process becoming thereby free from sulphur.

The cyclopentane produced under the conditions described is particularly pure and gives excellent performance as a fuel in a standard air-cooled aero-engine testing unit. This is indicated by comparison of the relative cyclopentane performance of 240 (in terms of lbs. per square inch B. M. E. P.) in a standard aeroengine testing unit as against a relative toluene performance of 170 (in the same terms). The physical properties of a representative sample of cyclopentane produced according to the process of the invention are as follows:

B. P. at 760 mm C 49.4

Cottrell spread Nil Sulphur content wt 0.0004

Octane number (C. F. R. motor method) 84 According to the invention moreover the crude concentrate with its content of dicyclopentadiene obtained by polymerisation of the crude benzole forerunnings with its content of cyclopentadiene, the concentrate having an approximate boiling range of C.-175 C. is advantageously treated e. g. with ammonium sulphidefor removal of carbon disulphide, and thereupon topped to remove the lightends boiling in the approximate boiling range of 73 C.- C. The light ends consist mainly of benzene with some unsaturated hydrocarbons and sulphur compounds, for example thiophen. The residue after removal of the light ends consists chiefly of dicyclopentadiene by reason of the ease with which such cyclopentadiene in the benzole iorerunnings is polymerised. The cyclopentadiene in the crude forerunnings may however be polymerised rapidly and successfully to dicyclopentadiene by contact with dilute acid. a

The dicyclopentadien may be obtained in a pure state by fractionation under vacuum in an eflicient column. The material is a solid in the form of colourless needle crystals at ordinary temperature and has a boiling point of 88.7 C. at 50 mm. pressure.

According to the invention moreover dicyclopentadiene may be de-polymerised at temperature of l55-170 C. which may be carried out in a column packed with ironturnings or similar material of iron or steel functioning as a catalyst and the overhead product taken off slowly at a column head temperature of 40 C.42 C. The overhead product of distillation and de-polymerisation is cyclopentadiene and is substanor tially sulphur-free. By suitable control of the distillation the rate of production of cyclopentadiene may be adjusted to the rate of hydrogenation in the hydrogenation units to which it passes. By such means intermediate storage and re-polymerisation to the dimeride are avoided.

The invention comprises the processing conditions hereinafter described.

In carrying the invention into effect the cyclopentadiene may advantageously be hydrogenated in the vapour phase over a hydrogenation-dehydrogenation catalyst of the molybdenum oxidealumina type, and under the following conditions:

Temperature 400 C.

Pressure 200 lbs/sq. in.

Oil input rate (total oil feed) 1.0 volumes/volume of catalyst/hour.

Hydrogen recycle rate 5000-6000 C. F./B.

of oil feed.

The feed is advantageously diluted with an inert material in such a proportion as to moderate or stabilise the reaction conditions. The presence of sulphur has however no deleterious effect on the molybdenum oxide-alumina hydrogenation catalyst and thus the previously removed light ends may conveniently be used as a moderating or stabilising diluent. Under these conditions the further advantage results that the benzene is refined in the same operation and the complete preliminary removal of carbon disulphide is thereby rendered unnecessary.

Alternatively cyclopentane, either as produced in the process described or derived from another source may be used as the moderating or stabilising diluent.

No limitation is involved to the use of the type of hydrogenation catalyst indicated. Thus the process may be carried out in the liquid phase in the use of a nickel catalyst at a temperature of from 50 C.-100 C. If Raney nickel however be used as the catalyst or any other catalyst liable to sulphur poisoning under the reaction conditions, it is necessary in order to avoid poisoning of the catalyst that the material processed should first be rendered sulphur-free. In such a case cyclopentane itself is a particularly advantageous moderating or stabilising diluent, and thus if it be desired to obtain a pure cyclopentane, cyclopentane itself may advantageously be used as diluent in preference to benzene, whereby the necessity of subsequent distillation to separate the benzene diluent is avoided.

The use of benzene has however substantial advantages as a diluent inasmuch as on its discharge from the process it is substantially free from sulphur as well as frome olefines, although it contains a small percentage (approximately of high boiling residue, probably derived from dicyclopentadiene. In this way the cyclopentadiene is hydrogenated and the benzene is refined in one operation. Furthermore where the ultimate object is to produce an aviation spirit blending constituent the mixture of benzene and cyclopentane after removal of the high boiling residue may together serve as an aviation fuel constituent without further treatment, the benzene being restricted to the permitted proporion that may be required by the specification. The conditions of hydrogenation referred to are such that the benzene is not itself hydrogenated.

We have found that during de-polymerisation a considerabl amount of the dicyclopentadiene.

appears to be further polymerised, resulting in an appreciable quantity of solid residue being left in the still. This residue may even amount to four times the amount of the residue remaining after vacuum distillation of crude dicyclopentadiene. The production of thes higher polymers we have found may be reduced appreciably by supplying the dicyclopentadiene to the depolymeriser substantially at the rate at which depolymerisation is required and that the de-pclymeriser itself should be no larger than is necessary for this purpose. In this way prolonged heating in the still is avoided.

It is known moreover that the polymerisation of the dicyclopentadiene is offset by packing the still with steel turnings or steel wool, whereby a large surface area of iron is thus provided which serves as a depolymerising catalyst.

Alternatively under the conditions indicated, the crude concentrate in the state of vapour and without preliminary removal of the light ends may be fed to a de-polymeriser consisting of a vessel packed with iron or steel wool or other convenient packing offering a large surface, and maintained at a temperature for example of 200 C.-300 C. and at a moderate pressure. The vapour leavin the depolymeriser may be condensed and fed to the hydrogenation unit as liquid, or the vapour may be mixed with hydrogen and passed together in vapour phase directly into a vessel containing an hydrogenation catalyst such as molybdenum oxide-alumina. This method of operation has the advantage that the benzene diluent is already present in the vapour and that no further dilution may be necessary.

Advantageous process conditions are indicated in the following examples:

Example 1.The light ends with their content of benzene was distilled from 388 liters of the crude concentrate resulting from polymerisation of benzol forerunnings. The greater part came over at atmospheric pressure, but in order to avoid overheating in the still and depolymerisation of dicyclopentadiene at this stage, the last traces were removed under vacuum at a temperature below the depolymerising temperature. The sulphur content of the light ends recovered as overhead was 0.102 per cent by weight, the original charge of concentrate was 388 litres and the light ends taken overhead to C.-208 litres.

The residu consisting chiefly of dicyclopentadiene was then heated to C. C. at atmospheric pressure when cyclopentadiene distilled off at 2.3 litres per hour.

The following were the physical properties of the cyclopentadiene produced:

B. P. at 760 In. In C 40.3

The cyclopentadiene was diluted with four times its volume of the light ends and this total oil feed passed over a 5% molybdenum oxide-onalumina catalyst at a temperature of 400 C., and a hydrogen pressure of 200 lbs/sq. in. The total oil feed over the catalyst was 1.0 v./v./hr. When a sufficient quantity of the hydrogenated product had been collected, this was used as a diluent for subsequent hydrogenations, the cyclopentadiene content of the feed to the hydrogenation unit always being maintained at 20% by volume. By constantly recycling the products, the cyclopentane content of the final material was approxi-- mately 60% by volume.

Litres Cyclopentadiene produced 99 Hydrogenation products 157 Cyclopentan'e produced 94 Refined benzol 63 The benzol during the processing was desulphurised (sulphur content 0.0007 per cent by weight), and contained approximately 5% of high boiling residue.

Example 2.--The crude material was dropped into a flask maintained in an oil bath at 240 C.-

250 C. By this means the light ends and dicyclo pentadiene were flashed off from a small amount of gummy residue. The vapours from this flask were passed through an iron tube of 56" in length, and an internal diameter of 1 /2", and the tube was packed with steel wool. The tube was electrically wound and the products were passed through a water-cooled condenser into a flask fitted with a solid CO2 trap. The material was passed through the tube at two difierent temperatures and at difierent rates. The following table gives the properties of the original material and the various products obtained:

Table Origina mate Run 1 Run 2 Run 3 Run 4 rial Conditions Temp. of tube O.. 210 290 300 290-300 290-300 Rate of addition of concentrate. .cc./hr 93 74 141 233 Vol. of concentrate/v01. of tube/hour 0. 186 0. 148 0. 282 0. 466

Properties of product Sp. gr. 60 F 0.9150 0. 8845 0. 8400 0. 8400 0.8380 I. B. P. C 75.5 56 46 47 47 79. 64 53 52. 52. 5 81. 0 66. 5 54. 5 54 54 84. 0 68. 5 55. 5 55 55 88.0 72 57. 5 57 56. 5 92. 5 76. 5 59. 5 59 58. 5 98. 0 81. 5 62. 5 62 61 109. 5 87 66 65. 5 64. 5 153. 0 94. 5 70 70 69 166. 5 120 75 75 74. 5 167. 5 167 I 80 80. 5 80 170.0 170 91 90. 5 88. 5 174. 5 176 173. 5 175 175. 5 Bromine number Francis) 212 221 252 249 260 726 g. of the product from run 4 was distilled, and the yield of cyclopentadiene was found to be 271 g., or 38 per cent by weight. This indicated that almost complete de-polymerisation had occurred, since the dioyclopentadiene content of the starting material was 39 per cent by weight. The mixture so obtained was fed as before to a hydrogenation unit, and the product were cyclopentane and refined benzol. 7

It will be seen from the table that 210 C. is not a suificiently high temperature to effect complete de-polymerisation under the conditions indicated, but the reaction was complete at all rates of addition used at 290 C.-300 C.

We claim:

1. A process for the production of cyclopentane from the benzol forerunnings of a coal tar distillate, comprising the steps of subjecting the fore runnings to polymerisation, and producing a concentrate having an approximate boiling range of to 175 C., distilling the said concentrate for the separation as overhead of the light ends boiling approximately at 78 to C., consisting of benzene mainly, together with some unsaturated and sulphur compounds, and a residue fraction as bottoms containing dicyclopentadiene, subjecting said residue fraction to a depolymerising operation to convert dicyclopentadiene in said fraction to cyclopentadiene, and directly subjecting cyclopentadiene so obtained to hydrogenation in the presence of a temperature moderating and reaction stabilising diluent, to yield the cyclopentane product, said depolymerising operation being carried'out in a column packed with iron or steel in a divided state such as small pieces or fibre to yield substantially sulphur-free cyclopentadiene as overhead at a column head temperature of 40 to 42 C. at a rate corresponding to the required feed rate of the cyclopentadiene in its hydrogenation.

2. A process for the production of cyclopentane from the benzol forerunnlngs of a coal tar distillate, comprising the steps of subjecting the forerunnings to polymerisation, and producing a concentrate having an approximate boiling range of 75 to C., distilling the said concentrate for the separation as overhead of the light ends boiling approximately at 78 to 80 C., consisting of benzene mainly, together with some unsaturated and sulphur compounds, and a residue fraction as bottoms containing dicyclopentadiene, subjecting said residue fraction to a depolymerising operation to convert dicyclopentadiene in said fraction to cyclopentadiene, and subjecting cyclopentadiene so obtained to hydrogenation in the presence of a temperature moderating and reaction stabilising diluent, to yield the cyclopentane product, said hydrogenation of the cyclopentadiene product being carried out in the use of a molybdenum oxide-alumina type of catalyst at a temperature of the order of 400 C., at a pressure of the order of 200 lbs. per square inch, at an input rate of the order of 1.0 volume/volume of catalyst/ hour in the presence of hydrogen in substantial excess of the proportion taking part in the reaction.

3. A process for the hydrogenation of cyclopentadiene for the production of cyclopentane, comprising diluting the cyclopentadiene with not substantially less than four times its volume of an inert diluent material to serve as a reaction temperature moderating and reaction stabilising diluent and carrying out the hydrogenation reaction in the use of a molybdenum oxide-alumina type of catalyst at a temperature of the order of 400 C., at a pressure of the order of 200 lbs. per square inch, at an input rate of the order of 1.0 Volume/ volume of catalyst/hour and in the presence of a quantity of hydrogen inthe proportion of at least 5000 cubic feet of hydrogen per barrel of feed, to yield the cyclopentane product.

STANLEY FRANCIS BIRCH. FREDERICK ARNOLD FIDLER. LESLIE SENIOR THORNES. 

